Plate heat exchangers, such as the brazed and plate and frame types, are typically used in refrigeration and air conditioning applications. A brazed plate heat exchanger is shown in U.S. Pat. Nos. 4,987,955 and 5,291,945. The heat exchangers, which are low in cost and relatively simple to make, can be used as evaporators, condensers, heat pumps, and a variety of other equipment.
A plate heat exchanger is made up of a series of stacked thermally conductive plates. In between the plates are channels. In an evaporator mode, a refrigerant fluid flows through the alternating channels. Heat transfer occurs from the other fluid across the plates. The refrigerant fluid is injected into the heat exchanger at one end and exits at the other end.
The problem with these type of heat exchangers is that the refrigerant may be a mixture of two phases, namely a liquid and a gas. A typical situation is when a heat exchanger is placed downstream of an expansion valve. The liquid separates from the gas, resulting in an uneven distribution throughout the exchanger. Gravity causes the separation. Some channels may receive mostly liquid, while other channels may receive mostly gas. Uneven distribution results in a loss of capacity and efficiency.
Therefore, it is desirable to provide a plate heat exchanger that maintains the distribution of a homogeneous two phase refrigerant flowing therethrough.